The Central Asian Flyway (CAF) is uniquely shaped by the Himalaya–Qinghai–Tibet Plateau complex—a major geographic feature that influences migratory route selection of waterbirds traveling between breeding grounds in northern Eurasia and Central Asia, and the Indian subcontinent, the primary non-breeding region of the CAF. Using published and unpublished telemetry data, we compiled and digitized unique migratory trajectories and applied line-density analyses standardized across species to identify recurrent migratory pathways and areas of convergence. We identified three broad migratory corridors: (i) the Western Asian Lowland Corridor (25°–40° N, 60°–72° E), which bypasses the Central Asian mountains to the west; (ii) the Pamir–Karakoram Corridor (32°–39° N, 74°–78° E), centred on the Upper Indus–eastern Hindu Kush–Pamir–Karakoram convergence zone; and (iii) the Eastern Himalayan Corridor (26°–37° N, 87°–100° E), encompassing routes through the Sikkim–Bhutan region of the Himalayas, the Brahmaputra Valley, and pathways circumventing the eastern Himalayas. In addition, emerging evidence highlights migration routes that do not conform to these generalized corridors, including direct high-altitude crossings of the Central Himalayan Region (27°–32° N, 78°–87°E), particularly among species such as Demoiselle Crane (Grus virgo), Brown-headed Gull (Chroicocephalus brunnicephalus), and Black-tailed Godwit (Limosa limosa). We interpret these corridors as generalized and flexible rather than fixed biological boundaries, with species and populations utilizing multiple corridors depending on geography, season, and migration strategy. Overall, this synthesis consolidates fragmented knowledge on waterbird migration within the CAF, identifies key data gaps, and provides a foundation for future research and improved conservation planning in a flyway where 51% of waterbird populations are declining.
Year-round territorial defense is crucial for reproductive success in many tropical birds. In these species, partners often coordinate their songs in duets to defend a shared territory. In this scenario, the pair members may behave according to different motivations and interests, or through essentially cooperative strategies. However, few studies have examined whether sex-specific roles in leadership and cooperation vary with the sex and spatial arrangement of intruders. The aim of this study was to experimentally investigate how the distance between intruders influences partner coordination in territorial defense in the Rufous Hornero (Furnarius rufus). We conducted playback experiments simulating intruder duets broadcast either from adjacent speakers (0.1 m apart) or from spatially separated speakers (∼12 m apart). We recorded the number, duration, and latency of songs, as well as the latency to approach within 20 m and 5 m of the speakers and the time spent by each individual within 5 m of them. Partners showed strong coordination across all approach and vocal behaviors, jointly approaching a single speaker when the speakers were spatially separated. Pairs responded more cautiously when the speakers were adjacent; however, responses did not differ according to the sex simulated by each speaker. Notably, when females led the vocal response, pair defense was biased toward female intruders. Overall, our findings support the joint territory defense hypothesis, highlighting the importance of pair cooperation and coordination in Rufous Hornero territorial defense.
